"Once you start down the dark path, forever will it dominate your destiny. Consume you, it will, as it did Obi Wan's apprentice."

"You must feel TheForce around you. Life creates it... makes it grow. Luminous beings are we, not this crude matter."

Somewhat RetConed, unfortunately, with the twaddle in ST1 about MitiChlorian?s.

"Adventure; excitement. A Jedi craves not these things."

"Fear leads to anger; anger leads to hate; hate leads to suffering."

"You will know the Dark Side from the Light when you are calm, at peace, and passive."

"Ow! Lying on my ear you are!"

Some of these "teachings" are pretty poisonous. The idea that we are "luminous beings" and not "crude" matter is at the core of dualism, which can lead to people committing heinous acts convinced that they are justified by some other "plane of existence" or "after-life".

Actually, the way Yoda speaks is based on Yiddish, a dialect of German (with additions from Hebrew and SlavicLanguages) spoken by Jews in Eastern Europe, and still spoken by some ultra-Orthodox (Chareidi) Jews today. The reason Yoda speaks English like that is GeorgeLucas (or maybe someone else who helped write StarWars' script, forgessen :-) ) had encountered a quote from IsaacAsimov saying that it would be impossible for one to view someone speaking English in Yiddish's grammatical order as threatening. This of course was important for creating a strange being that would look like an alien to adults but not be frightening to children.